一、什么时候配置whenIF SGA >= 2GB AND sessions >= 500THENenabling HugePages becomes a requirement on Linux 64-bit system.
二、怎么配置How to Configure HugePagesStep 3: If you have Oracle Database 11g or later, the default database created
uses the Automatic Memory Management (AMM) feature which is incompatible
with HugePages. Disable AMM before proceeding. To disable, set the
initialization parameters MEMORY_TARGET and MEMORY_MAX_TARGET to 0
(zero). Please seeDocument 749851.1 for further information in case you encounter the error below:
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$ ./hugepages_settings.sh
...
Recommended setting: vm.nr_hugepages = 1496
$
Note: You can also calculate a proper value for the parameter
yourself but that is not advised if you do not have extensive experience
with HugePages and concepts.
Step 5: Edit the file /etc/sysctl.conf and set the vm.nr_hugepages parameter there:
...
vm.nr_hugepages = 1496
...
This will make the parameter to be set properly with each reboot.
Step 6: Stop all the database instances and reboot the server
(Although
settings could have been done dynamically they would not be effective
to the extent we require before a reboot. The best practice is to do a
persistent system configuration and perform a reboot to complete the
configuration as presented through the steps above)
# grep HugePages /proc/meminfo
HugePages_Total: 1496
HugePages_Free: 485
HugePages_Rsvd: 446
HugePages_Surp: 0
The values in the output will vary. To make sure that the configuration is valid, theHugePages_Free value should be smaller thanHugePages_Total and there should be someHugePages_Rsvd.HugePages_Rsvd counts free pages that are reserved for use (requested for an SGA, but not touched/mapped yet).
The sum ofHugepages_FreeandHugePages_Rsvd may be smaller than your total combined SGA as instances allocate pages dynamically and proactively as needed.
四、计算大页Shell Script to Calculate Values Recommended Linux HugePages / HugeTLB Configuration
1.[root@wang ~]# vi hugepages_settings.sh
--添加如下脚本
#!/bin/bash## hugepages_settings.sh## Linux bash script to compute values for the# recommended HugePages/HugeTLB configuration# on Oracle Linux## Note: This script does calculation for all shared memory# segments available when the script is run, no matter it# is an Oracle RDBMS shared memory segment or not.## This script is provided by Doc ID 401749.1 from My Oracle Support# http://support.oracle.com# Welcome textecho "This script is provided by Doc ID 401749.1 from My Oracle Support(http://support.oracle.com) where it is intended to compute values forthe recommended HugePages/HugeTLB configuration for the current sharedmemory segments on Oracle Linux. Before proceeding with the execution please note following: * For ASM instance, it needs to configure ASMM instead of AMM. * The 'pga_aggregate_target' is outside the SGA and you should accommodate this while calculating SGA size. * In case you changes the DB SGA size, as the new SGA will not fit in the previous HugePages configuration, it had better disable the whole HugePages, start the DB with new SGA size and run the script again.And make sure that: * Oracle Database instance(s) are up and running * Oracle Database 11g Automatic Memory Management (AMM) is not setup (See Doc ID 749851.1) * The shared memory segments can be listed by command: # ipcs -mPress Enter to proceed..."read# Check for the kernel versionKERN=`uname -r | awk -F. '{ printf("%d.%d\n",$1,$2); }'`# Find out the HugePage sizeHPG_SZ=`grep Hugepagesize /proc/meminfo | awk '{print $2}'`if [ -z "$HPG_SZ" ];then echo "The hugepages may not be supported in the system where the script is being executed." exit 1fi# Initialize the counterNUM_PG=0# Cumulative number of pages required to handle the running shared memory segmentsfor SEG_BYTES in `ipcs -m | cut -c44-300 | awk '{print $1}' | grep "[0-9][0-9]*"`do MIN_PG=`echo "$SEG_BYTES/($HPG_SZ*1024)" | bc -q` if [ $MIN_PG -gt 0 ]; then NUM_PG=`echo "$NUM_PG+$MIN_PG+1" | bc -q` fidoneRES_BYTES=`echo "$NUM_PG * $HPG_SZ * 1024" | bc -q`# An SGA less than 100MB does not make sense# Bail out if that is the caseif [ $RES_BYTES -lt 100000000 ]; then echo "***********" echo "** ERROR **" echo "***********" echo "Sorry! There are not enough total of shared memory segments allocated forHugePages configuration. HugePages can only be used for shared memory segmentsthat you can list by command: # ipcs -mof a size that can match an Oracle Database SGA. Please make sure that: * Oracle Database instance is up and running * Oracle Database 11g Automatic Memory Management (AMM) is not configured" exit 1fi# Finish with resultscase $KERN in '2.2') echo "Kernel version $KERN is not supported. Exiting." ;; '2.4') HUGETLB_POOL=`echo "$NUM_PG*$HPG_SZ/1024" | bc -q`; echo "Recommended setting: vm.hugetlb_pool = $HUGETLB_POOL" ;; '2.6') echo "Recommended setting: vm.nr_hugepages = $NUM_PG" ;; '3.8') echo "Recommended setting: vm.nr_hugepages = $NUM_PG" ;; '3.10') echo "Recommended setting: vm.nr_hugepages = $NUM_PG" ;; '4.1') echo "Recommended setting: vm.nr_hugepages = $NUM_PG" ;;esac# End"hugepages_settings.sh" [New] 94L, 3254C written[root@wang ~]#2.[root@wang ~]# chmod +x hugepages_settings.sh3.[root@wang ~]# ./hugepages_settings.sh.........................省略..............Press Enter to proceed...Recommended setting: vm.nr_hugepages = 102404执行后会有输出建议值。
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